Apparatus for retreading tires

ABSTRACT

The specification discloses an apparatus for retreading a tire casing with a precured and premolded tire tread. The apparatus includes a flexible envelope which surrounds the tire and precured tread assembly from sidewall to sidewall to form with the walls of a multipart chamber device a fluid tight annular chamber surrounding the tread portion of the assembly. The apparatus includes means for inflating the interior of the assembly to laterally distend the sidewalls of the casing into engagement with sealing means mounted on the inner walls of the multipart chamber device.

United States Patent [191 Reppel [111 3,779,833 [45] Dec. 18, 1973APPARATUS FOR RETREADING TIRES [75] Inventor:

[731 Assignee: Oliver Tire and Rubber Company,

Oakland, Calif.

[22] Filed: Apr. 25, 1972 [21] Appl. No.: 247,488

Related US. Application Data [63] Continuation of Ser. No. 883,161, Dec.8, 1969,

Willi E. Reppel, Lewiston, Maine abandoned. v

[52] US. Cl 156/394, 156/96, 264/36, 264/315, 264/316, 425/19, 425/39,425/43, 425/45 [51] Int. Cl B2911 5/04, B29h 5/18 [58] Field of Search156/96, 394; 264/36, 264/313, 314, 315, 316; 425/D1G. 19, 39, 43, 44, 45

[ 5 6 1 References Cited UNITED STATES PATENTS 2,014,010 9/1935 Wheatley156/394 FM 2,459,757 1/1949 Smith 156/96 X 3,207,647

9/1965 Schelkmann 1. 156/394 X 2,904,842 Alm 156/394 X 3,486,198 12/1969Lewis 2,501,577 3/1950 Pfeiffer 2,746,515 5/1956 Usack Skidmore 156/96Primary Examiner-Alfred L. Leavitt Assistant Examiner-C. B. CosbyAttorney-William D. Hall et a1.

[5 7] ABSTRACT The specification discloses an apparatus for retreading atire casing with a precured and premolded tire tread. The apparatusincludes a flexible envelope which surrounds the tire. and precuredtread assembly from sidewall to sidewall to form with the walls of amultipart chamber device a fluid tight annular chamber surrounding thetread portion of the assembly. The apparatus includes means forinflating the interior of the assembly to laterally distend thesidewalls of the casing into engagement with sealing means mounted onthe inner walls of the multipart chamber device.

16 Claims, 10 Drawing Figures PATENTEDUEC18 I975 SHEET 10F 5 INVENTORWILLI E. REPPEL PATENTEDnEc 18 1975 SHEET 2 0F 5 INVENTOR WILLI E. REPPEL APPARATUS FOR RETREADING TIRES This is a continuation ofapplication, Ser. No. 883,161, filed Dec. 8, 1969, now abandoned. Thiscontinuation application is copending with U.S. Ser. No. 182,602; U.S.Ser. No. 182,603; and U.S. Ser. No. 182,814, all of which weredivisional applications of the parent U.S. application U.S. Ser. No.883,161.

BRIEF SUMMARY OF THE INVENTION Generally speaking, there are two methodsof retreading aworn-out tire to make it suitable for continued use. Theyare retreading a tire in a standard tire retreading mold, and moldlessretreading.

Tires to be retreaded in molds are buffed and covered with a layer ofuncured rubber, and placed into a standard tire retreading mold. In themold, the rubber is shaped into the desired tread pattern bypressurizing the inside of the tire and heating the entire assemblyuntil the uncured rubber is cured, formed and bonded to the old casingby a combination of heat and pressure.

The problem with retreading a tire in a standard retreading mold residesin the fact that the finished tread will quickly wear in use. This isbecause the layer of uncured rubber cannot be subjected to extremelyhigh molding pressures and temperatures while being vulcanized withoutpermanently deforming or distorting the casing. Any deformation ordistortion during the curing operation will subsequently tend to ruptureor weaken the vulcanized bond between the cured and molded tire 'treadand the carcass itself. Any excessive temperature also tends to weakenand deteriorate the tire carcass which was previously cured.

Moldless retreading, on the other hand, uses a strip of precured andpremolded tread which is usually supplied in a long, continuous stripfrom an extrusion and molding process. This precured and preformed stripof tread material is, in a sense, vulcanized before it is applied to thetire casing, as considerably higher vulcanization pressures andtemperatures may be applied while the strip is being molded'without thetire carcass. This results in a tread surface which will have improvedstrength and density and which will resist normal road abrasion. I

In this method, the worn-out tire is treated by a buffing machine as inthe molding operation, and the precured and premolded tread rubber isapplied to the buffed casing with a layer of uncured raw rubber compoundtherebetween. The tire is then wrapped up in an adjustable thin steelband and inflated and the entire assembly is heated and cured in apressurized and heated chamber.

An alternate form of moldless retreading with the tread strips that areprecured and premolded utilizes a flexible rubber envelope thatcontinuouslycovers the outside of the tire when the tire is mounted on atire rim. The entire assembly is again inserted into a pressurized andheated chamber, but the envelope gives a uniform pressure to the treadand casing and assists in giving a uniform and continuous bond whileassisting in the removal of any possible air bubbles.

This method of moldless retreading requires the operator to invest inexpensive equipment to utilize the new premolded and precured tread.

The present invention makes it possible to utilize the precured andpremolded tread that has become popular in an existing standard tireretreading mold. In addition, the invention allows retreading of varioussized tires within a single size tire retreading mold. The presentinvention utilizes a mold liner to seal the interior of the mold and agasket means to seal various sized tires within the mold.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a partial cross section of astandard tire retreading mold, as fitted for use in retreading a tirewith a precured and precast tread;

FIG. 2 is an enlarged partial cross section of a standard tireretreading mold, and the mold liner used therein;

FIG. 3 is a plan view of the gasket sealing means used in the presentinvention;

FIG. 4 is an isometric view of the tire assembly prepared for retreadingas it is inserted into a standard tire retreading mold;

FIG. 5 is an exploded cross-sectional view of the entire assembly andapparatus;

FIG. 6 is a partial cross-sectional view of a new and improvedadjustable mold, as adapted for retreading of various sized tires;

FIG. 7 is a cross sectional view of a new and improved mold;

FIG. 8 is a layered, sectional, and isometric view of a tire assemblyprepared for retreading, an air bleeding means, and the inner moldliner; and

FIG. 9 is a cross-sectional view of a new and improved mold forretreading tires.

FIG. 10 is a cross sectional view of a retreading apparatus and a tireassembly prepared for retreading, wherein said assembly is mounted on arim DETAILED DESCRIPTION OF THE DRAWINGS Referring to FIG. 1, a worn-outtire casing 11 has been prepared for retreading by buffing it on abuffing machine to remove any of the old tread design. The buffing notonly cleans the surface of the casing but roughens it in preparation forthe bonding and vulcanizing processes to follow. A liberal coating of asolvent or rubber cement is applied to the'roughened casing. Anotherlayer of solvent or rubber cement is applied to the under surface of thepremolded and precured tread strip 13. The underside of this tread stripis also buffed or manufactured with a pre-roughened surface. The rubbercement or solvent is utilized to hold the tire assembly prepared forretreading together before it is placed in the tire retreading mold. Acuring bag 14 is placed within the tire and partially inflated. Theentire assembly is then enveloped with a nylon mesh air bleeding means61, and an inner envelope 60. This assembly is then placed within astandard tire retreading mold 15 which has been lined with mold linerl6, and a seal is affected between the mold liner l6 and envelope bymeans of gasket members 17 and 18.

Pressure is applied to the inside and outside of the tire casing byinflating the curing bag 14 with hot air or steam through nozzel 19.Simultaneously, air pressure or hydrostatic pressure is applied to thechamber 20 maintained between the tire prepared for retreading and themold liner by means of valve member 21 and- /or 22. Pressure in thecuring bag and in chamber 20 may vary between 20 and 200 pounds persquare inch. A lower pressure will extend the lifetime of the curingbag, envelope and mold liner, but it may cause the bad adhesion betweenthe components of the tire prepared for retreading. The mold lineritself is suitable for maintaining a pressure of 200 pounds per squareinch, and the curing bag 14 is normally maintained at a pressure higherthan that maintained in chamber by the standard inflation differencethat is normally maintained in the tire. In one typical example, if thetire is designed to operate at pounds of pressure in normal use, chamber20 will be inflated to 75 pounds per square inch and the curing bag toapproximately 100 pounds per square inch. Thus, there is an effectiveadhesion pressure of 75 pounds per square inch forcing the tread layer13 towards carcass 11.

Alternately, as illustrated in FIG. 10, the tire may be mounted on a rim170 and inflated with a standard, inner tube 171 before it is placed inthe mold. In this application, however, the air pressure utilized may besomewhat reduced.

The temperatures utilized typically range between 150F. to 300F.,depending upon the technical properties of the used casing. Generallyspeaking, a high temperature makes for a short curing time but mayimpair the quality of the casing. A low temperature does not generallyaffect the tire casing itself but does unduly extend the curing time.The temperature is generated by supplying 300 pressurized air or steamto curing bag 14 through nozzel 19. High temperature at the exterior ofthe casing will result from circulating 300 air or steam in chamber 20by introducing it through inlet 21 and exhausting it through inlet 22.Additionally, the heating apparatus in the standard tire retreading mold15 may be utilized, and steam or hot air will be circulated throughpassages 23 and 24 or as in the case of an electric mold, the heatingelement of the standard tire retreading apparatus may be energized.

The tire retreading is finished when the uncured layer of rubber I2 isvulcanized and fully bonded to casing 11 and tread member 13. Thisvulcanization process completes the cure of tread member 13, if it is apartially cured tread, but in any event vulcanizes the tread, adhesionlayer, and carcass into a unitary assembly.

Referring to FIG. 5, the mold liner consists of a plurality of layers.The first layer 25 extends over the tire assembly prepared forretreading from sidewall to sidewall to form an effective seal betweenthe mold'liner and the standard tire retreading mold. A second and thirdlayer 26 and 27 are applied on top of the first layer to cover the treadmolding area generally designated at on mold 15. A fourth layer 28 isapplied over the top of the two layers 26 and 27 to cover them and bondthe four layers into a single mold assembly. Layers 25 and 28 are formedof a thin flexible nonthermoplastic material; whereas layers 26 and 27are formed of relatively thick uncured layers of raw rubber. Shortlengths of steel bands or cords 29 may be inserted between layers 26 and27 to strengthen and provide some structured rigidity for the moldliner.

It will be noted in FIG. 2 that the mold 15 is split into two sections15a and 15b. Similarly, the mold liner 16 is split at 32 and gasket 33is applied to one side of the mold liner. Layer 33 is a soft curedflexible layer that seals against the opposing section of the mold linerto prevent passage of any fluids therebetween.

There are two problems inherent in utilizing the mold liner which mustbe balanced against each other to achieve satisfactory operation. Thefirst problem is transferring the heat that may be generated in mold 15through the mold liner and into the interior chamber 20. The otherproblem is the reusability of the mold liner, and in providing for itsease of insertion. Ifa relatively hard layer were used adjacent thetread pattern 30, very little heat would be transferred because it wouldcover the actual tread channels and ridges that normally provide a muchlarger heat transfer surface. In such case, the only heat transfer wouldbe across the general uppermost area of the tread pattern.

If a soft flexible material is utilized, the material will fill thetread pattern completely, filling the voids such as indicated as 30a andwill be cured in that position by the temperature and pressure of thevulcanized process. Although the soft material will utilize all of theheat transfer surface, it then becomes extremely difficult to separatethe mold liner from the mold casing 15, and almost impossible toreinsert the mold liner for further use. Therefore, the presentmulti-layered mold liner has been found to be an equitable balance tosolve the two problems. Utilizing the relatively thick, soft uncuredrubber layers 26 and 27, the rubber will migrate into the tread pattern30 as illustrated in FIG. 2, thereby increasing the effective heattransfer surface of the mold liner. Using a relatively thin, non-thermalplastic layer 28 which is already cured, prevents the relatively softlayers 26 and 27 from migrating into void 30a, and enables the operatorto remove the mold liner after the curing operation is completed, and toinsert it for furture use with a minimum amount of effort. The insertedmold liner halves normally stay in the proper mold half if the operatorretreads several tires in the same apparatus. They are removed only ifmold is reutilized for conventional retreading.

The mold liner is necessary to effectively seal air passages 35 that areutilized in the standard retreading mold to allow the raw uncured rubberto migrate into the tread pattern 30.

An interior envelope is shown in cross section in FIG. 8, draped aboutcarcass l1 and thread cap 13. This interior envelope is placed about thetire assembly prepared for retreading before it is placed in the mold.Sandwiched between the tire assembly prepared for retreading and theenvelope is air bleeding means 61. This air bleeding means may be formedof a wovenmesh cloth such as a nylon mesh or the like and allows the airtrapped between the tire assembly prepared for retreading and the innerenvelope to migrate from the trapped cavities to the ambient airpressure at 62. Inasmuch as the gasket and sealing means generallycontact the inner envelope at the dotted line illustrated at 63 the airbleeding means 61 effectively provides an air passageway from the cavitybetween the interior envelope and the tire assembly to the outsideatmosphere. In this way, any air trapped in the tire assembly or betweenthe tire assembly and the envelope liner is expelled when the pressurein chamber 20 is raised above the ambient atmospheric air pressure.

The purpose of the inner envelope 60 is two-fold. First, it enables theair pressure to be applied uniformly over the tread-capped surfacethroughout the curing process. If the tire were placed in the tireretreading assembly without the envelope, the air present between layers11 and 13, when subjected to the heat, would expand causing the treadlayer 13 to lift from the carcass. Once the tread cap lifts from thecarcass, without the envelope, the air in chamber 20 at that pressureenters the joint between tire carcass 11 and tread cap 13 and providesequal pressure on both sides of tread cap 13, thereby assisting thenatural resiliency of the tread cap and allowing it to become separatedfrom the tire carcass. In this manner, the inner envelope 16 not onlydistributes pressure evenly from the cap to the carcass but alsoprevents any of the high pressure air present in chamber 20 fromentering into the sealing region between the carcass 11 and tread cap 13to thereby destroy the bond.

The second purpose of the interior envelope is to provide an effectiveescape route through the nylon mesh 61 for any air that is trapped inthe seal between air carcass l1 and the tread member 13.

Referring again to FIG. 5, it will be noted that gasket members 17 and18 illustrate an alternate construction from that illustrated in FIG. 1.The present invention enables the owner of a standard tire retreadingapparatus illustrated as to utilize the new premolded and precured tiretread in retreading tires. It also enables the operator to retread avariety of different sizes of tires by use of spacer members 36 and 37illustrated on gaskets 17 and 18. Thus, an operator may adapt his moldto as many as four cross sectional sizes below the cross sectional sizeof the tire mold. The largest size tire that may be utilized with themold liner would be one size below the mold size. A plurality of beadsizes may also be used, i.e., 6.50-14; 6.70-l4; 7.00-14, so that inactuality if three cross sectional sizes and four bead sizes are used,the total number of combinations would be twelve. Spacer members 36 and37 enable the operator to utilize a plurality of head sizes by insertingthe appropriately sized bead spacer as illustrated in FIG. 3. The gasketsealing means 17 comprises spacer member 36, annular support member 38,inlet means 21, exhaust means 39, and means for providing an airpressure reading of the interior chamber 40. In actuality, the functionsof 21, 39 and 40 are interchangeable, with the inlet and exhaust beingsupplied to either and the pressure gauge being supplied to any one ofthe three. The end of inlet, pointing into chamber may be provided witha jet, injecting air or steam in a tangential direction into chamber 20for better circulation. This prevents any localized hot spots that mightotherwise distort the carcass and result in an uneven cure. Alternately,only one such gasket means such as 17 need be used, asthe tire sidewall41 illustrated at FIG. 1 will form an effective seal between layer andwall member 42 without the necessity of using gasket member 18.

When two gasket sealing members such as 17 and 18 are utilized, theinlets 21, 39 and and gaskets member 17 will be used as supply, and theinlets generally designated as 22 in gasket member 18 will be used asexhaust, with one of the inlet members or exhaust members being utilizedas a pressure reading station.

FIG. 4 is an isometric view of a tire assembly prepared for retreadingabout to be inserted into a standard tire retreading mold apparatus.Mold liner 16 is shown inserted in the illustrated mold half. The treadpattern 43 illustrated on flexible envelope 60 results from previousapplication of heat and pressure. The

two halves of mold liner 16 are joined together along seam 32 as theother half of the tire retreading mold illustrated as 15b in FIG. 5 (notshown in FIG. 4) is closed and latched to tire mold apparatus 15 A newand improved form of the present invention is illustrated in FIGS. 6 and7, wherein a treadless mold 115 is utilized with a single layer flexibleenvelope 160 to retread a tire carcass 111 with a premolded and precasttread member 113. It will be noted that the envelope 160 now formschamber 120 between the mold 115 and envelope 160 rather than betweenenvelope 160 and tire carcass 111. Gasket means 150 provides aneffective seal for mold 115 between the respective halves 115a and 115bto provide an airtight chamber 120. Passageways 123 and 124 are for thecirculation of hot air, steam or other type temperature fluids, or an analternative embodiment, passageways 123 and 124 may be replaced withelectric heating means. A curing bag 114 is utilized in this new andimproved embodiment in the same manner in which it was utilized in astandard tire retreading apparatus. Alternatively, as illustrated inFIG. 10, a tire mounted on a rim with a conventional inner tube could beused in place of the curing bag. Gasket members 117 and 118 may besimplified somewhat in that air passageways 121 and 122 are now ventedthrough the wall of chamber 1 15 rather than through the gasket members117 and 118. Recesses 151 and 152 are provided in the interior wall ofmold 115 through sealing gasket members 117 and 118.

It will be noted that FIG. 6 is a partial cross section of the new andimproved mold of the present invention, whereas FIG. 7 is a full crosssection. Removing the tread pattern or tread base from the interior ofmold 115 has two primary advantages: first, it eliminates the somewhatcomplex mold liner required for use in the standard tire retreading moldand secondly, it allows an additional cross sectional size of tire to beused. In the apparatus disclosed in FIGS. 6 and 7 four cross sectionalsizes may be used with a number of bead sizes whereas in a standard tireretreading mold, only three cross sectional sizes may be used. Thenumber of bead sizes that maybe adapted remain the same for each type ofapparatus. In FIG. 7, it will be noted that mold has access holes 153and 154 to assist in the assertion of the circulating fluids to nozzle119 or curing bag 114 and to assist the utilization of the standard moldloading equipment used to load and center the tire assembly prepared forretreading in the mold. In actual practice, and appropriately sizedgasket and spacer 136 is utilized to adapt each of the vaious sized beadsizes to the mold liner. The outer parts 155 of spacer 136 and the outerpart 55 of spacer 36 in FIG. 5 form annular ridges to assist inproviding an airtight seal between spacer 136 and envelope 160 orbetween spacer 36 and tire carcass 11. The pressure for sealing chamberis provided by inflation of curing bag 114, pressing tire sidewall 111and envelope 116 against spacer 136 as well as outer part 155. Thisforces the tire against portion to effect an air tight seal. a

FIG. 9 illustrates another alternate and improved embodiment of myinvention. It has been found that this embodiment is much easier,simpler and more inexpensive to manufacture than a standard retreadingmold, and is readily adaptable to various sized tire carcasses. The basemember 215 is a flat annular disk member provided with strengtheningribs (not shown) to adequately disperse the tensions between the centralsupport 266 and the outer rim noted at 267. Another flat annular diskmember 268 is provided with four (4) stiffening rims such as thoseillustrated at 269, 270 and 271. The third component of my new andimproved tire retreading assembly is annular ring member 272 which isprovided with air inlet means 273 and air outlet means 274. Chamber 220is sealed by means of a flat annular gasket member 275 which seals notonly the annular ring member 272, but also the tire side wall as shownat 216. An alternate sealing means is illustrated at 276 wherein anannular O-ring is provided in the outer extremity of ring member 272 toengage disk member 268 in a sealing arrangement.

With this embodiment, the operator may retread four or five tires ofdifferent cross sectional sizes with a single annular ring member 272.If on the other hand, the operator desires to retread a differentcross-sectional size, such as 6.50 rather that 8.50, he needs onlyreplace the annular ring member 272. In this manner it then becomesunnecessary to have more than one retreading apparatus; With my presentinvention, the only things needed to encompass an entire range of tiresizes are disk members 215 and 268 and a plurality of annular ringmembers 272 in different sizes.

It should be pointed out that sealing means 276 is an alternate form ofthe invention and may be utilized on both sides of ring member 272, orin the alternative, the annular gasket member 216 could be utilized onboth support members, 215 and 268 to provide for effective gasketsealing on both sides for both the tire assembly prepared for retreadingand the annular ring member 272.

Lug nut 277 is used to tighten the assembly and to provide effectivesealing pressure against the seal gasket members 276 and 275 and therebyprovide an airtight chamber 220.

ln the operation of my device, lug nut 277 is removed and the upper diskportion 268 is removed. The tire assembly prepared for retreading, andits inner envelope 60 and air bleeding means 61 are placed into the tireassembly as shown in HO. 9 and approximately centered therein. The upperdisk portion 268 is then replaced and the entire assembly tightened withlug nut 277 to provide an effective air-tight seal in chamber 220. Asource of high pressure, high temperature fluid such as steam isconnected to fluid inlet 273 and 219 to provide an effective sealingdifferential pressure between chamber 220 and curing bag 214. It will benoted that air inlet 273 is angled in a circumferential direction, so asto cause the steam introduced into chamber 220 to circulate throughoutthe chamber ina circumferential direction before exiting at fluid exit274. This prevents the steam inlet from focusing on any small portion ofthe tire assembly prepared for retreading and thereby prevents anyuneven curing that might result therefrom. As pointed out previously,any air trapped between the tire carcass 211 and tread member 213 iseffectively released by means of bleeding means 261 which is placedbetween inner envelope 260 and tire assembly 211. Inasmuch as the nylonmesh member 261 communicates with the ambient outside air pressure at280, the differential pressure between chamber 220 and the outside airpressure will effectively drive any trapped air therein to the outsideambient air. a

It is to be understood that, although several preferred embodiments ofthe invention have been shown in the drawings and described withconsiderable particularity in the foregoing specification, the inventionis not limited to the specific details and forms shown and described,but includes all modifications coming within the scope of the inventedclaims and their equivalents.

I claim:

1. Apparatus for retreading tires with a precured premolded tread stripcomprising a. a multipart rigid shell for holding a tire and precuredtread assembly, said shell having a generally annular shape with aU-shaped cross section, said shell defining a sealed chamber above thetread of the assembly,

b. a thin flexible envelope adapted to cover said assembly from sidewallto sidewall around its outer perimeter,

c. sealing means on the inner wall of said shell adjacent each of saidsidewalls for providing a seal between the flexible envelope and theannular shell at the sidewalls of the assembly, said sealing meanscooperating with the inner walls of said multipart shell and theexterior surface of said envelope to provide a fluid tight seal for saidchamber between said shell and said envelope,

d. fluid inlet and exhaust means for providing pressurized and heatedfluid within the annular chamber defined between said sheet and saidenvelope,

e. inflatable means mounted for inflation within the interior of saidassembly, said means inflated to a pressure greater than the pressure insaid annular chamber, said means laterally distending the sidewalls ofsaid assembly to contact said sealing means,

f. means mounted between said assembly and said envelope for evacuatingair trapped between the surface of the tire assembly prepared forretreading and said thin flexible envelope.

2. Apparatus for retreading tires comprising:

a. a treadless, two-part torroidal mold having a generally U-shapedcross-section, said mold having a fluid inlet and a fluid exhaust means,said fluid inlet means being disposed tangentially within said mold todirect said fluid tangentially of said tire in a swirling circularmanner,

b. a thin flexible envelope mounted within said mold for covering a tireassembly prepared for retreading from sidewall to sidewall around itsouter perimeter;

c. sealing means for sealing each side of said flexible envelope to saidtorroidal mold along the sidewall of a tire assembly prepared forretreading to thereby create an annular chamber between said liner andsaid mold, said sealing means defining two annular members interfittedwith said two part torroidal mold, one of said members being interfittedon each side of said tire;

d. curing bag means for mounting within said tire assembly, said curingbag means defining at least one inlet means for inflating the interiorof said tire assembly to a pressure equal to or greater than thepressure in said annular chamber, said curing bag contacting the innersurface of said tire assembly from a point on the inner sidewallopposite one of said sealing means to a point on the other side of saidinner sidewall opposite the other of said sealing means, said curing bagalso defining a lateral member extending laterally within said tire froma point opposite one of said sealing means to a point opposite saidother sealing means.

3. Tire retreading apparatus as claimed in claim 2 wherein said sealingmeans further comprise an annular support member, and an annular spacingportion to space the sealing portion of said gasket means axially fromthe annular support member of the gasket.

4. Tire retreading apparatus as claimed in claim 2 which furthercomprises an air bleeding means mounted between said thin flexibleenvelope and said tire assembly prepared fro retreading.

5. Apparatus for retreading tires as claimed in claim 1 wherein saidinflatable means defines a curing bag means with at least one fluidinlet means for inflating said curing bag means to a pressure greaterthan the pressure in said annular chamber.

6. Apparatus for retreading tires as claimed in claim 1 wherein saidinflatable means comprises a rigid rim for supporting the tire and aninner tube inside the tire andaround the rim with an inlet means forinflating said tube to a pressure greater than the pressure in saidannular chamber.

7. Apparatus for retreading tires as claimed in claim 1 wherein saidmeans for sealing the flexible envelope comprises annular sealing meansmounted on the inner sidewalls of said annular mold.

8. Apparatus for retreading tires as claimed in claim 5 wherein saidcuring bag means provides support for the inner surface of said tireassembly from a point radially aligned with or radially inwardly fromsaid sealing means on one inner sidewall of said mold to a point on theother inner sidewall of said mold opposite the other of said sealingmeans.

9. Apparatus for retreading tires as claimed in claim 9 wherein saidsealing means comprises annular undulations which extend inwardly tocontact the tire assembly prepared for retreading.

10. Apparatus for retreading tires as claimed in claim 8 wherein saidmeans for inflating the interior of said tire assembly further comprisesa lateral means to support said curing bag means, said lateral meansextending laterally within said tire from a point opposite or radiallyinwardly of one of said sealing means to a point opposite said othersealing means.

11. Apparatus for retreading tires as claimed in claim 1 wherein saidmulti-part mold defines first and second sidewalls and first and secondannular connecting members, said connecting members joining togethermidway between said sidewalls to form said annular mold.

12. Apparatus for retreading tires as claimed in claim 1 wherein saidsealing means comprise at least one annular ridge which extends inwardlyto contact the tire assembly prepared for retreading.

13. Apparatus for retreading tires with a precured premolded tread stripcomprising a. a treadless, two part rigid toroidal enclosure having agenerally U-shaped cross section and defining a generally annular sealedchamber around the tread of the assembly,

b. a thin flexible envelope adapted to cover said assembly from sidewallto sidewall around its outer perimeter,

c. sealing means defined on the inner wall of said enclosure adjacenteach of said assembly sidewalls, said sealing means defining at leastone annular ridge adjacent each of said sidewalls for providing a sealbetween the flexible envelope and the enclosure at the sidewalls of theassembly, said ridges, and the inner walls of said enclosure cooperatingwith the exterior surface of said envelope to provide a fluid tightannular chamber around the tread of the assembly,

d. fluid inlet and exhaust means for admitting pressurized and heatedfluid into said annular chamber defined between said enclosure and saidenvelope,

e. inflatable means mounted within said assembly for inflation to apressure greater than the pressure in said annular chamber, said meanslaterally distending the sidewalls of said assembly to urge them intocontact with said sealing ridges,

f. means mounted between said assembly and said envelope for evacuatingair trapped between the surface of the tire assembly prepared forretreading and said thin flexible envelope.

14. Apparatus for retreading tires as claimed in claim 13 wherein saidinflatable means comprises a rigid rim for supporting said tire assemblyand an inner tube within said assembly, said tube having an inlet meansto provide inflation of said tube to a pressure greater than thepressure in said annular chamber.

15. Apparatus-for retreading tires as claimed in claim 13 wherein saidinflatable means comprises a curing bag means with at least one fluidinlet for inflating said curing bag means to a pressure greater than thepressure in said annular chamber.

16. Apparatus for retreading tires as claimed in claim 13 wherein saidsealing means also comprises axial spacing means for laterally adjustingthe ridges defined on said sealing means.

2. Apparatus for retreading tires comprising: a. a treadless, two-parttorroidal mold having a generally U-shaped cross-section, said moldhaving a fluid inlet and a fluid exhaust means, said fluid inlet meansbeing disposed tangentially within said mold to direct said fluidtangentially of said tire in a swirling circular manner, b. a thinflexible envelope mounted within said mold for covering a tire assemblyprepared for retreading from sidewall to sidewall around its outerperimeter; c. sealing means for sealing each side of said flexibleenvelope to said torroidal mold along the sidewall of a tire assemblyprepared for retreading to thereby create an annular chamber betweensaid liner and said mold, said sealing means defining two annularmembers interfitted with said two part torroidal mold, one of saidmembers being interfitted on each side of said tire; d. curing bag meansfor mounting within said tire assembly, said curing bag means definingat least one inlet means for inflating the interior of said tireassembly to a pressure equal to or greater than the pressure in saidannular chamber, said curing bag contacting the inner surface of saidtire assembly from a point on the inner sidewall opposite one of saidsealing means to a point on the other side of said inner sidewallopposite the other of said sealing means, said curing bag also defininga lateral member extending laterally within said tire from a pointopposite one of said sealing means to a point opposite said othersealing means.
 3. Tire retreading apparatus as claimed in claim 2wherein said sealing means further comprise an annular support member,and an annular spacing portion to space the sealing portion of saidgasket means axially from the annular support member of the gasket. 4.Tire retreading apparatus as claimed in claim 2 which further comprisesan air bleeding means mounted between said thin flexible envelope andsaid tire assembly prepared fro retreading.
 5. Apparatus for retreadingtires as claimed in claim 1 wherein said inflatable means defines acuring bag means with at least one fluid inlet means for inflating saidcuring bag means to a pressure greater than the pressure in said annularchamber.
 6. Apparatus for retreading tires as claimed in claim 1 whereinsaid inflatable means comprises a rigid rim for supporting the tire andan inner tube inside the tire and around the rim with an inlet means forinflating said tube to a pressure greater than the pressure in saidannular chamber.
 7. Apparatus for retreading tires as claimed in claim 1wherein said means for sealing the flexible envelope comprises annularsealing means mounted on the inner sidewalls of said annular mold. 8.Apparatus for retreading tires as claimed in claim 5 wherein said curingbag means provides support for the inner surface of said tire assemblyfrom a point radially aligned with or radially inwardly from saidsealing means on one inner sidewall of said mold to a point on the otherinner sidewall of said mold opposite the other of said sealing means. 9.Apparatus for retreading tires as claimed in claim 9 wherein saidsealing means comprises annular undulations which extend inwardly tocontact the tire assembly prepared for retreading.
 10. Apparatus forretreading tires as claimed in claim 8 wherein said means for inflatingthe interior of said tire assembly further comprises a lateral means tosupport said curing bag means, said lateral means extending laterallywithin said tire from a point opposite or radially inwardly of one ofsaid sealing means to a point opposite said other sealing means. 11.Apparatus for retreading tires as claimed in claim 1 wherein saidmulti-part mold defines first and second sidewalls and first and secondannular connecting members, said connecting members joining togethermidway between said sidewalls to form said annular mold.
 12. Apparatusfor retreading tires as claimed in claim 1 wherein said sealing meanscomprise at least one annular ridge which extends inwardly to contactthe tire assembly prepared for retreading.
 13. Apparatus for retreadingtires with a precured premolded tread strip comprising a. a treadless,two part rigid toroidal enclosure having a generally U-shaped crosssection and defining a generally annular sealed chamber around the treadof the assembly, b. a thin flexible envelope adapted to cover saidassembly from sidewall to sidewall around its outer perimeter, c.sealing means defined on the inner wall of said enclosure adjacent eachof said assembly sidewalls, said sealing means defining at least oneannular ridge adjacent each of said sidewalls for providing a sealbetween the flexible enVelope and the enclosure at the sidewalls of theassembly, said ridges, and the inner walls of said enclosure cooperatingwith the exterior surface of said envelope to provide a fluid tightannular chamber around the tread of the assembly, d. fluid inlet andexhaust means for admitting pressurized and heated fluid into saidannular chamber defined between said enclosure and said envelope, e.inflatable means mounted within said assembly for inflation to apressure greater than the pressure in said annular chamber, said meanslaterally distending the sidewalls of said assembly to urge them intocontact with said sealing ridges, f. means mounted between said assemblyand said envelope for evacuating air trapped between the surface of thetire assembly prepared for retreading and said thin flexible envelope.14. Apparatus for retreading tires as claimed in claim 13 wherein saidinflatable means comprises a rigid rim for supporting said tire assemblyand an inner tube within said assembly, said tube having an inlet meansto provide inflation of said tube to a pressure greater than thepressure in said annular chamber.
 15. Apparatus for retreading tires asclaimed in claim 13 wherein said inflatable means comprises a curing bagmeans with at least one fluid inlet for inflating said curing bag meansto a pressure greater than the pressure in said annular chamber. 16.Apparatus for retreading tires as claimed in claim 13 wherein saidsealing means also comprises axial spacing means for laterally adjustingthe ridges defined on said sealing means.